Process for producing glycolide and glycolic acid oligomer for production of glycolide
a technology of glycolic acid and oligomer, which is applied in the field of process for producing glycolide and glycolic acid oligomer for production of glycolide, can solve problems such as adverse effects, and achieve the effect of lowering the reaction velocity and viscosity of the system
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synthesis example 1
Synthesis of Glycolic Acid Oligomer (a)
[0095]Into a 500 ml-glass-made vessel, 800 g of the above-obtained high-purity glycolic acid aqueous solution was charged and heated up to 200° C. under stirring at normal pressure to proceed with condensation while distilling out resultant water. Then, the pressure in the vessel was lowered to 5.0 kPa and held at 200° C. for 2 hours to distill off low-boiling point fractions including non-reacted glycolic acid, thereby preparing 400 g of glycolic acid oligomer (a) containing impurity carboxylic acids (A) at a concentration calculated as diglycolic acid (x) of 0.16 wt. % and nitrogen-containing substances (B) at a concentration calculated as ammonia (y) of 0.0002 wt. % giving an effective concentration (x+100y) of depolymerization-obstructing substances of 0.18 wt. %.
synthesis example 2
Synthesis of Glycolic Acid Oligomer (b)
[0096]A solution was prepared by adding glycoloamide (made by Aldrich Co.) so as to provide a concentration of 0.1 wt. % to the above-prepared high-purity glycolic acid aqueous solution. The procedure of Synthesis Example 1 was repeated except for using the solution instead of the high-purity glycolic acid aqueous solution per se to obtain glycolic acid oligomer (b). The nitrogen content in glycoloamide is 19 wt. % so that 0.1 wt. % of glycoloamide correspond to 0.02 wt. % of ammonia on an equi-molar basis, and it was multiplied by a condensation ratio of 2(=800 g / 400 g) to provide a nitrogen content calculated as ammonia in the oligomer (b) of 0.04%. Thus, the glycolic acid oligomer (b) contained impurity carboxylic acids (A) at a concentration calculated as diglycolic acid (x) of 0.16 wt. % and nitrogen-containing substances (B) at a concentration calculated as ammonia (y) of 0.04 wt. % giving an effective concentration (x+100y) of depolymeri...
synthesis example 3
Synthesis of Glycolic Acid Oligomer (c)
[0097]The procedure of Synthesis Example 1 was repeated except for using the above-mentioned commercially available glycolic acid aqueous solution instead of the high-purity glycolic acid aqueous solution to obtain glycolic acid oligomer (c) containing impurity carboxylic acids (A) at a concentration calculated as diglycolic acid (x) of 10.6 wt. % and nitrogen-containing substances (B) at a concentration calculated as ammonia (y) of 0.005 wt. % giving an effective concentration (x+100y) of depolymerization-obstructing substances of 11 wt. %.
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